CHICAGO – Runners in Sunday’s Chicago Marathon held a city nearly a thousand miles away close to their hearts and were determined to show that, six months after the Boston Marathon bombings, they could pound the streets together without fear.

Tightened security along the route changed the atmosphere perceptibly from past years, but the crisp, cool weather helped many set personal records in the first major marathon in the United States since the Boston bombings.

Runners from more than 120 countries and all 50 states observed a moment of silence for the victims and families before the race kicked off. Three people died and more than 260 were injured in the April 15 bombings.

Clara Santucci, who finished ninth Sunday and was tops among U.S. women, said the boost in security made getting to the starting line more difficult than for an any race she’d run before.

“I understand with this being the next major marathon after Boston (in the United States) the concern for security,” Santucci said. “I just hope they figured it out so that spectators aren’t kept from being able to see the most exciting parts of the race, like the finish and the start. That’s what our sport’s all about.”

Among the extra precautions in Chicago were Homeland Security vehicles parked on a sidewalk on Michigan Avenue near the lakefront and bomb-sniffing police dogs walking the area. City snow removal trucks were repurposed to block closed roadways.

The finish line, targeted in the Boston bombings, drew special scrutiny as course marshals asked runners to show their race numbers as they neared the 26.2-mile race’s end.

The mood was mostly buoyant. Police clapped and wished runners luck. Spectators clanged cowbells and shouted support to friends and strangers.

Memories of Boston raised the resolve of many runners. The bombings brought Chicago dentist Jim Ryan back into the marathon fold. He thought he was done, but started training again after the attack.

“After what happened, I decided that day I was going to qualify,” said Ryan, who ran the race dressed as the character Luigi from the Super Mario Brothers video game. He missed a qualifying time in two other races earlier this year, but qualified Sunday to run Boston in 2015.

“Boston is my second favorite city to run in for a marathon. Chicago, of course, is first,” he said. “Who knows? Maybe I’ll go there (Boston in 2014) and be a spectator. I love that city.”

The enhanced security made it more difficult for Jo Ann Surman of Chicago to meet her daughter right at the finish line, but they chose another meeting spot — and didn’t mind. Surman wore a Boston Red Sox shirt.

“I just wanted to put this on today to let other people see that we still think of them,” she said, referring to the victims and Boston residents in general.

Spectator Nicole Ioffe of Batavia, Ill., donned a bright green sparkly wig to cheer on her friend, Yvette Fratzke. Despite the wacky costume, she said thoughts of the Boston bombing weren’t far from her mind.

“It made me think twice about coming down here to do this. ... I’m going to this amazing event and I had to worry about something like that happening to innocent people,” she said Sunday morning after cheering Fratzke at the 2.5-mile mark. “Life is too short and I can’t live in constant fear.”